Circuit apparatus



April 7, 1936. J. A, COMSTOCK AL 2,036,399

CIRCUIT APPARATUS Filed Nov. 30, 1934 INVENTOR. hmesA.flomtock& M'IliamW Gimstazzg.

11. M Q) 9/. ATTORNH Patented Apr. 7, 1936 UNITED STATES PATENT OFFICECIRCUIT APPARATUS -.of Indiana Application November 30, 1934, Serial No.755,328

11 Claims. (Cl. 175-3655) Our invention relates generally to electricalapparatus, and more particularly to electrical systems for convertingunidirectional current into alternating or pulsating current.

An object of our invention is the provision of an electrical system toenergize an electrical load. having a variable resistance.

Another object of our invention is to provide for energizing anelectrical load having a variable resistance from a direct currentsource by utilizing the combination of a high leakage reactancetransformer and an interrupter for causing current to fiowintermittently in the primary winding of the transformer.

A further object of our invention is the provision of a high leakagereactance transformer and an interrupter for causing current to flowintermittently into the primary winding of the transformer to energizean electrical load having a variable resistance, wherein the interrupterand the high leakage reactance transformer mutually cooperate in suchmanner that the interrupter is protected from being over loaded by theaction of the transformer limiting the value of the intermittent currentflowing to the primary winding, when the resistance of the electricalload decreased.

A still further object of our invention is to provide for decreasing theenergization of the coil which controls the interrupter, after theinterrupter is set in operation.

Another object of our invention is the provision of a high leakagereactance transformer having two secondary windings for energizing anelectrical load having a variable resistance and an interrupter forcausing current to flow intermittently in the primary winding, whereinthe action of the high leakage reactance transformer is such that, whenthe resistance of the electrical load decreases, the value of theintermittent current flowing to the primary winding is limited toprotect the interrupter from being overloaded.

A still further object of our invention is the provision of a balanced,high leakage reactance transformer having three magnetic shunts and twosecondary windings, in which an electrical load having a variableresistance is connected across each of the secondary windings, and aninterru ter for causing current to flow intermittentiy in the primarywinding, wherein the action of the high leakage reactance transformer issuch that, 'in the event one or both of. the secondary windings isshorted, or when the resistance of one or both of the electrical loadsdecreases, the value of the intermittent current flowing to' the primarywinding is limited to protect the interrupter from being over loaded.

A further object of our invention is the provision of an autotransformer and an interrupter, wherein the interrupter is protectedfrom'being overloaded by the action of the auto transformer limiting thevalue of the intermittent current flowing to energize the autotransformer.

A further object of our invention is to provide for preventing arcing ofthe contacts of the interrupter.

Other objects and a fuller understanding of our invention may be had byreferring to the following description, taken in conjunction with theaccompanying drawing, in which like reference characters designate likeparts, and in which;

Figure 1 is a diagrammatic view of an electrical system embodying thefeatures of our invention.

Figure 2 is a diagrammatic view of a modified form of our invention, inwhich an auto transformer is utilized.

Figure 3 is a diagrammatic viewof another modified form of ourinvention, wherein a double secondary winding high leakage reactancetransformer is employed, and

Figure 4 is a diagrammatic view of another form of our invention inwhich a balanced high leakage reactance transformer is employed.

With reference to Figure 1 of the drawing, our invention comprises ingeneral, a high leakage reactance transformer 9 having a split primarywinding with two winding portions l3 and It, and a split secondarywinding with two winding portions 16 and I1, an interrupter it having avibrating contact 2'! and two stationary contacts 28 and 29, and anactuating coil 25.

As diagrammatically illustrated, the transformer 9 includes a magneticcore 8 I, and a magnetic shunt 2| disposed between the primary winding,and the secondary winding. The magnetic shunt 2! is so proportioned anddesigned that it ofiers a higher reluctance to the passage of the fluxthan the magnetic core II. The increased reluctance of the magneticshunt 2| may be accomplished either by varying the cross sec tional areathereof, or by utilizing air gaps between the ends of the magnetic shuntand the inside walls of the magnetic core H. The secondary winding,which may be constructed of the two parts l6 and I! has the adjacentends of the two windings l6 and M joined together, and connected to aground i 8. The outer ends 01' the two windings l6 and I! are connectedin circuit relation with a gaseous tube I9.

While we have illustrated a gaseous tube, it is to be understood thatour invention is not limited to such showing, as our invention may beutilized to energize electrical load of all kinds having a variableresistance. The primary winding, which may be constructed of two partsi3 and I8 is arranged to be intermittently energized from the directcurrent supply source, indicated by the positive conductor 38 and thenegative conductor 38.

While any suitable means may be employed to intermittently energize theprimary windings i3 and N, we preferably utilize an interrupter of thevibrating tuned type. As illustrated, the vibrating contact 21 iscarried by a resilient finger 22 having its lower end stationarilymounted upon a support 3i Mounted upon the upper end of the resilientfinger 22, is an armature 26 magnetically actuated to the left, asviewed in the drawing, when the coil 25 is energized. The stationarycontact 28 is carried upon a flnger 23 having its lower end thereofstationarily mounted upon a support 30. The stationary contact 29 is,similarly, mounted upon a finger 28 having its lower end thereofstationarily mounted in a support 32.

The lamp 33 is of the type in which its cold resistance is lower thanits hot resistance. A lamp having these characteristics is found in theso called tungsten lamps. The purpose of this lamp is to allow morecurrent to flow through the coil 25 during the period that the vibratingarmature is being brought up to its resonant condition, than that whichflows after it reaches its resonant condition. This is because, duringthis period, it requires more current to actuate the vibrating armature26 than it does after the vibrating armature 26 reaches its resonantcondition. By the time the vibrating armature 26 reaches its resonantcondition, the filament of the lamp 33 becomes hot, which is accompaniedby an increase in its resistance, with the result that the flow of thecurrent in the coil 25 is accordingly decreased. In this manner, thecoil 25 is prevented from being over heated, as would be the case if thecurrent flowing through the coil 25 were not decreased, by the action ofthe lamp 33.

In explaining the operation of our invention, let it be assumed that theknife switch 31 has been just closed. Upon the closing of the knifeswitch, the current flows in the following manner: Beginning with thepositive supply conductor 38, the current flows through the upper sideof the switch 31, the conductors 41, 48, 49 and 58, the lamp 33, thecoil 25, the conductor 5|, the primary winding l3 to the mid-point 52,the conductor 53, and through the lower side of the switch 31 to thenegative supply'conductor 39. Upon the establishment of this circuit,the magnetic flux produced by the current flowing through the current 25attracts the vibrating armature 26 to the left, as viewed in thedrawing, until the vibrating contact 21 engages the stationary contact28. As is noted, just as soon as the vibrating contact 21'engages thestationary contact 28, the coil 25 is shunted and thus deenergized. Thismeans that, the current now flows in the following manner: Beginningwith the positive supply conductor 38, the current flowsthrough theupper side of the switch 31, the conductors 41 and 48, the vibratingcontact 21, the stationary conductor 28', the conductors 54 and 5|, theprimary winding l3 to the midpoint 52, the conductor 53, and through thelower side of the switch 31 to the negative supply conductor 39. Just assoon, however, as the vibrating contact 21 engages the stationarycontact 28, which deenergizes the coil 25, the resiliency of thevibrating finger 22 causes the vibrating armature26 to swing to theleft, as viewed in the drawing, until the vibrating contact 21 engagesthe stationary contact 29. Just as soon as the vibrating contact 21emgages the stationary contact 28, the flow of the current may be tracedas follows: Beginning with the positive supply conductor 38, the currentflows through the upper side of the switch 31, the conductors 41 and 48,the vibrating contact 21, the stationary contact 29, the conductor 55,the primary winding H to the mid-point 52, the conductor 53 and thelower side of the switch 31 to the negative supply conductor 39. Afterthe vibrating contact 21 engages the stationary contact 29, thevibrating armature 26 is again attracted by the flux produced by thecoil 25, because the current, which was previously interrupted, againflows through the coil 25 just as soon as the vibrating contactdisengages the stationary contact 28. The attractive force of the coil25 causes the vibrating contact 21 to swing to the left, as viewed inthe drawing, and again engage the stationary contact 28. This operationis repeatedly continued, and within a very short period, the vibratingarmature 26, rapidly gains momentum and reaches its resonant condition,after which the vibrating contact 21 vibrates between the two stationarycontacts 29 and 28 at a substantially uniform rate, which may bedetermined by the design of the various cooperatively associated parts.The condenser 35, which is connected across the vibrating contact 21 andthe stationary contact 28, serves to minimize the arcing, which wouldotherwise take place upon the interruption of the circuit. Similarly,the condenser 36, which is connected across the vibrating contact 21 andthe stationary contact 29, serves to minimize the arcing which wouldptherwise take place upon the interruption of the circuit. The condenser38, which is connected in parallel with the coil 25, tends to give agood smooth current flow through the coil 25.

As just previously noted, the action of the in-' terrupter i8 causesrapid reversals of the current flowing through the primary winding l3and the primary winding Id. In other words, an alternating flux is setup in the magnetic core H of the transformer 9. The action of thealternating flux cutting the secondary windings l6 and I1, produces arelatively high initial secondary voltage to ionize the gas in thegaseous tube l9. However, when the gaseous tube is once ionized, the

resistance thereof, immediately decreases to a relatively low value.This tends to cause a relatively large secondary current to flow, but itis noted that, as the secondary current tends to increase, there isestablished a relatively large secondary flux which opposes the passageof the primary flux. Accordingly, a, portion of the primary flux isby-passed through the magnetic shunt 2i. This means that the voltageinduced in the secondary windings is reduced to a relatively low value,with the result that the current flowing through the secondary circuitis maintained or limited at its operating normal value. Inasmuch, as thefunction of the magnetic shunt 2| tends to limit the value of thesecondary current, it likewise follows that the value of theintermittent current impressed upon the primary windings of thetransformer is accordingly limprinciple, it-is possible to utilize aninterrupter of the tuned vibrating type, which would other wise beimpossible to utilize with an ordinary transformer, for the reasonthatwhen the gas of the gaseous tube i9 once becomes ionized, theincreased amount of intermittent current which would flow to the primarywindings would be so great as to damage the contacts. It is also pointedout, that by utilizing the magnetic shunt principle; the periodicity ofthe vibrating contact may vary through a fairly large range, for thereason that the frequency of the interrupted current can be taken careof in the. design of the high leakage reactance transformer.

To minimize further the arcing upon the interruption of the current atthe contact points of the interrupter [9, we employ the combination of acondenser 40 and a discharge resistor 4|. Upon the interruption of theprimary current, there is a tendency for the current flowing througheither one of the two primary windings, as the case may be, to continueto flow in the same direction as it was previously flowing prior to theinterruption. Therefore, the primary current, during the period that thecontacts are opened, is urged to flow throughthe discharge resistor 4|,as well as, at the same time, temporarily charging the condenser 46,which is soon dissipated through the resistor 4|. While we have shownthe combination of a condenser and a discharge resistor 4!, we also findfrom actual tests, that the resistor may be used by itself, or thecondenser 49 may be used by itself.

In Figure 2, we utilize an auto, high leakage reactance transformer 60instead of the high leakage reactance transformer shown in Figure 1. Asillustrated the auto transformer comprises a split primary winding 6|, asecondary winding 62 and a magnetic shunt 63. The operation of theelectrical system, as shown in Figure 2, is substantially the same asthat described with reference to Figure 1, and the action of themagnetic shunt 63 is such that; when once the gas of the gaseous tube 64is ionized, the value of the intermittent current flowing to the primarywinding iii of the auto transformer, is limited to prevent overloadingand damaging of the vibrating contacts.

In Figure 3, we utilize a high leakage reactance transformer 65 of adifferent type. As shown, this transformer comprises a magnetic core Ii,two secondary windings 66 and 61, a split primary winding 68, and twomagnetic shunts 69 and 10. The split primary winding 68 isintermittently energized by the interrupter IS, in the same manner asthat described with reference to Figure l.

The inner ends of the two secondary windings 66 and 61 are joinedtogether and connected to a suitable ground 12. Each of the outer endsof the secondary windings is connected, respectively, to the upper endof two gaseous tubes 13 and 14. The lower ends of the two gaseous tubesare joined together and connected to the ground 12 by a conductor 15.With this arrangement, each of the gaseous tubes 13 and M are energizedindependently by its corresponding secondary winding.

Immediately upon the energization of the split primary winding 68, thereis established a primary flux which flows around the entire magneticcore ll, withsubstantially none of the flux flowing through the magneticshunts 69 and 16. The

primary flux induces a relatively high initial voltage in both thesecondary windings 66 and 61, which ionizes the gas and thus illuminatesthe two gaseous tubes 13 and 14. Just as soon as the gas of the tubes isionized, their electrical resistance immediately becomes relatively low,and thus a relatively large secondary current tends to flow through thesecondary windings 66 and 61. Consequently, with a sudden' rise in thesecondary current, the secondary windings 66 and 6! establish asecondary flux that opposes the passage of the primary flux through thesecondary windings. Because of the opposition of the secondary flux, 2.portion of the primary flux is constrained to flow through the twomagnetic shunts 69 and 10. The by-passing of the primary flux reduces-the voltage induced in the primary windings 66 and 61 to a value whichbears a relation to that portion of the primary flux still interlacingthe secondary windings. ondary voltage, in turn, limits the value of theswondary current. The degree to which the secondary current is limited,depends upon the reluctance of the magnetic" shunts 69 and I0, and uponthe design and proportions of the various other co-acting parts of thetransformer. The result and effect of the two magnetic shunts 69 and 10is such that after the gas of the gaseous tube is ionized, therelatively high initial second- .ary voltage is immediately, andautomatically reduced to its normal operating value. Inasmuch as theaction of the shunts 69 and I0 tend to limit the value of the secondarycurrent, it likewise follows that the value of the intermittent currentimpressed upon the split primary winding is accordingly limited, whichprotects the contacts from being damaged or overloaded.

By reason of the fact that the gaseous tubes 13 and M are respectivelyenergized by the secondary windings 66 and 61, it is possible to keepone of the gaseous tubes operating in its normal manner, even though theother gaseous tube may be grounded, which would cause a short upon itscorresponding secondary windings. In this connection, let it be assumedthat a ground occurs at the upper end of the gaseous tube 14. This meansthat the secondary winding 61 is now short circuited, and that thesecondary current of the secondarywinding 61 immediately tends to riseto a high value, which if not limited to a safe value, will burn out thesecondary windings and the contacts of the interrupter l0. Under thisshort circuited condition, the magnetic shunt 10 by-passes substantiallyall or a major part of the primary flux emanating from the primarywinding 68, with the result that the voltage induced in the secondarywinding 6'! is relatively low. This limits the current flow of the shortcircuited secondary winding 61, which, in turn, prevents the interruptedcurrent supplied to the primary windings from becoming excessive andburning the contacts of the interrupter I6.

Inasmuch as the magnetic shunt l0 by-passcs substantially all or a majorpart of the primary flux, the secondary winding 66 continues to operateand illuminate the gaseous tube 13. This means that one of the gaseoustubes is kept in operation, even though the other gaseous tube isgrounded; while, at the same time, preventing an excessive load imposedupon the interrupter l6.

In Figure 4, we illustrate an arrangement of a balanced, high leakagereactance transformer. The general construction and operation of theThis reduction in the sectransformer 19 is somewhat similar to the transformer 65, shown in Figure 3, except that there is a third magneticshunt disposed between the two parts of the split primary winding. Inthe operation of this transformer, the action of the two outer magneticshunts ii and 82 is substantially the same as that described withreference to the magnetic shunts 69 and II of Figure 3, and thus eitherone of the two gaseous tubes may be kept in operation, even though theother gaseous tube may be inoperative. The action of the third magneticshunt 00 will now be described. The reluctance of the magnetic shunt IIis relatively high as compared to the reluctance of the magnetic shuntsBI and 82, and thus, substantially no fluxflows through the magneticshunt 80 so long as the electrical load of each of the secondarywindings 83 and N is the same. But in the event that the electrical loadof the secondary windings 83 and 8 become unbalanced, the magnetic shunt80 by-passes a certain portion of the flux, as well as either one of thetwo shunts 8| and 82; depending, however, upon which one of thesecondary windings is overloaded. In other words, the magnetic shunt 80,or what may be termed a balancing shunt, is adapted, when the twosecondary windings 83 and II have substantially the same value of thesecondary flux opposing the passage of the primary flux, to by-pass arelatively small amount of the primary flux, and is adapted, when thetwo secondary windings have an unequal value of secondary flux opposingthe passage of the primary flux to by-pass a larger amount of theprimary flux. This, in turn, protects the contact points of theinterrupter from being overloaded or damaged.

From the foregoing description, it is noted that we have so combined ahigh leakage reactance transformer with an interrupter in such a. mannerthat the value of the intermittent current impressed upon the primarywinding of the transformer is limited to a safe value, which preventsthe overloading of the contacts, when the resistance of the electricalload decreases.

Although we have described my invention with a certain degree ofparticularity, it is understood that the present disclosure has beenmade only by way of example and that numerous changes in the details ofconstruction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

We claim as our invention:

1. A system for converting direct current into alternating current andfor utilizing said alternating current to energize an electrical loadhaving a variable resistance comprising, in combination, a magneticcore, a secondary winding disposed to surround a portion of the magneticcore, said portion being designated as a secondary core portion, aprimary winding associated with the secondary winding and disposed tosurround another portion of the magnetic core, intermittent means forrepeatedly interrupting the flow of the direct current and causing sameto flow intermittently in the primary winding, and magnetic shunt meanshaving a relatively high reluctance disposed between the primary windingand the secondary winding, said magnetic shunt means being adapted, whenthe secondary core portion has a relatively low secondary flux 0pposingthe passage of the primary flux, to bypass a relatively small amount ofthe primary flux, thereby causing the induction of a relatively highvoltage in the secondary winding, and being adapted, when the secondarycore portion has a relatively high secondary flux, opposing the passageof the primary flux, to by-pass a relatively large amount of the primaryflux, thereby reducing the voltage induced in the secondary winding,with the result that the reluctance of the secondary core portion variessubstantially inversely with changes in the resistance of the electricalload to protect the intermittent means from being overloaded by limitingthe value of the intermittent current flowing to the primary winding.

2. A system for converting direct current into alternating current andfor utilizi the said alternating current to energize an ele trical loadhaving a variable resistance comprising, in combination, a magneticcore, a secondary winding disposed to surround a portion of the magneticcore, said portion being designated as a secondary core portion, aprimary winding associated with the secondary winding and disposed tosurround another portion of the magnetic core, a tuned vibratinginterrupter for repeatedly interrupting the flow of the direct currentand causing same to flow intermittently in the primary winding, andmagnetic shunt means having a relatively high reluctance disposedbetween the primary winding and the secondary winding, said magneticshunt means being adapted, when the secondary core portion has arelatively low secondary flux opposing the passage of the primary flux,to bypass a relatively small amount of the primary flux, thereby causingthe induction of a relatively high voltage in the secondary winding, andbeing adapted, when the secondary core portion has a relatively highsecondary flux opposing the passage of the primary flux, to bypass arelatively large amount of the primary flux, thereby reducing thevoltage induced in the secondary winding, with the result that thereluctance of the secondary core portion varies substantially inverselywith changes in the resistance of the electrical load to protect thetuned vibrating in terrupter from being overloaded by limiting the valueof the intermittent current flowing to the primary winding.

3. A system for converting direct current into alternating current andfor utilizing the said alternating current to energize a plurality ofeleotrical loads having a variable resistance comprising, incombination, a magnetic core, a secondary winding disposed to surround aportion of the magnetic core, said portion being designated as asecondary core portion, a second secondary winding associated in spacedrelation with the firstmentioned secondary winding and disposed tosurround another portion of the magnetic core, said portion beingdesignated as the second secondary core portion, a primary windingassociated with the secondary windings and disposed to surround anotherportion of the magnetic core, intermittent means for repeatedlyinterrupting the flow of the direct current and causing same to flowintermittently in the primary winding, means for grounding one end ofeach of the secondary windings, means for connecting an electrical loadbetween the grounding means and each of the other ends of the secondarywindings, thus energizing one of the electrical loads by thefirstmentioned secondary winding and the other electrical load by thesecond-mentioned secondary winding, and two magnetic shunt means eachhaving a relatively high reluctance and each being disposed between theprimary winding and each of the secondary windings, the arrangement oithe magnetic core and the magnetic shunt means being adapted such that,when the value of the secondary flux of each of the two secondary coreportions opposing the passage of the primary iiux is unequal resultingfrom an unequal load distribution upon the two secondary windings orfrom a short circuited condition of the like imposed upon one of thesecondary windings, the magnetic shunt, which is disposed between theprimary winding and the secondary winding surrounding the secondary coreportion having the high secondary flux opposing the passage of theprimary flux, by-passes a larger amount of the primary flux than doesthe other shunt means, thereby causing less primary flux to interlacethe secondary winding surrounding the secondary core portion having thehigher secondary flux opposing the passage of the primary flux, and toinduce a lower voltage therein which protects the intermittent meansfrom being overloaded by limiting the current flowing through the saidsecondary winding having the lower resistance loador short circuitedcondition, and causing the primary flux to interlace the secondarywinding surrounding the secondary core portion having the lowersecondary flux opposing the passage of the primary flux and' to induce avoltage therein to keep the said secondary winding in operation forenergizing its electrical load.

4. A system for convertingdirect current into alternating current andfor utilizing the said alternating current to energize an electricalload having a variable resistance comprising, in combination, a magneticcore, a two part primary winding disposed to surround a portion of thecore, a secondary winding associated in spaced relation with the primarywinding and disposed to surround another portion of the core, saidportion being designated as the secondary core portion, intermittentmeans for repeatedly interrupting the flow of the direct current andcausing same to flow intermittently-in the primary winding, a magneticshunt disposed between the primary winding and the secondary winding,said magnetic shunt being adapted, when the secondary core portion has arelatively low secondary flux opposing the passage of the primary fluxproduced by the primary winding to by-pass a relative small amount ofthe flux produced'by the primary winding, thereby causing the inductionof a relatively high voltage in the secondary winding, and said magneticshunt being adapted when the secondary core portion has a relativelyhigh secondary flux opposing the passage of the primary flux produced bythe primary winding to by-pass a larger amount of the flux produced bythe primary winding, thereby reducing the voltage induced in thesecondary winding with the result that the reluctance of the secondarycore portion varies substantially inversely with changes in theresistance of the electrical load to protect the intermittent means frombeing over loaded, a second secondary winding associated in spacedrelation with the primary winding and disposed to surround anotherportion of the core, said portion being designated as thesecond-mentioned secondary core portion, a second magnetic shuntdisposed between the primary winding and the second-mentioned secondarywinding, said second-mentioned magnetic shunt being adapted, when thesecond-mentioned secondary core portion has a relatively low secondaryflux opposing the passage of the primary flux produced by the neticshunt being adapted, when the second-men- V tioned secondary coreportion has a relatively high secondary flux opposing the passage of theprimary flux produced by the primary winding, to by-pass a larger amountof the flux produced bythe primary winding, thereby reducing the voltageinduced in the second-mentioned secondary winding with the result thatthe reluctance of the second-mentioned secondary core portion variessubstantially inversely with changes in the resistance of the electricalload, to protect the intermittent means from being over loaded, and abalancing magnetic shunt disposed between the two parts of the primarywindings, said balancing shunt being adapted, when the two secondarycore portions have substantially the same value of secondary fluxproduced by the primary windi .ing to by-pass a relative small amount ofthe flux produced byrthe primary winding, and said balancing shunt beingadapted, when the two secondary core portions have an unequal value ofsecondary flux opposing the passage of the flux produced by the primarywinding to by-pass a larger amount of the flux produced by the primarywinding, thereby causing a relatively small amount of the said primaryflux to interlace the secondary winding surrounding the secondary coreportion having the, higher value of opposing secondary flux and toinduce a relatively low voltage therein, to protect the intermittentmeans from being overloaded, and causing a relatively large amount ofthe said primary flux to interlace the said secondary windingsurrounding the secondary core portion having the lower value ofopposing secondary flux, and to induce a relative 1y high voltage in thesaid secondary winding and thus keeping the said secondary winding inoperation for energizing its electrical load.

5. A system for converting direct current into alternating current andfor utilizing the said alternating current to energize an electricalload having. a variable resistance comprising, in combination, amagnetic core, a two part primary Winding disposed to surround a.portion of the core, a secondary winding associated inspaced relationwith the primary winding and disposed to surround another portion of thecore, said portion being designated as the secondary core portion,intermittent means for repeatedly interrupting the flow of the directcurrent and causing same to fiow intermittently in the primary winding,a magnetic shunt disposed between the primary winding and the secondarywinding, said magnetic shunt being adapted, when the secondary coreportion has a relatively low secondary flux opposing the passage of theprimary flux produced by the primary winding, to by-pass a relativesmall amount of the flux produced by the primary winding, therebycausing the induction of a relatively high voltage in the secondarywinding, and said magnetic shunt being adapted when the secondary coreportion has a relatively high secondary flux opposing the passage of theprimary flux produced by the primary winding, to by-pass a larger amountof .the flux produced by the primary winding, thereby reducing thevoltage induced in the secondary winding with the result that thereluctance of the secondary core portion varies substantially inverselywith changes in the resistance of the electrical load,

. over loaded. a second. secondary ciated in spaced relation with theprimary winding and disposed to surround another portion 0! the core,said portion being designated as the second-mentioned secondary coreportion, a second m agnetic shunt disposed between the second mentionedprimary winding, and the secondmentioned secondary winding, saidsecond-mentioned magnetic shunt being adapted, when the second-mentionedsecondary core portion has a relatively high secondary flux opposing thepassage of the primary-flux produced by the primary winding to by-pass arelatively small amount of the flux produced by the primary winding,thereby causing the induction of a, relatively high voltage in thesecond-mentioned secondary winding, and said second-mentioned magneticshunt being adapted, when the second-mentioned secondary core portionhas a relatively high secondary flux opposing the passage of the primaryflux produced by the second-mentioned primary winding to by-pass alarger amount of the flux produced by the primary winding, therebyreducing the voltage induced in the second-mentioned secondary windingwith the result that the reluctance of the second-mentioned secondarycore portion varies substantially inversely with changes in theresistance of the electrical load to prevent the intermittent means frombeing overloaded. Y

6. A system for converting direct current into alternating current andfor utilizing the said alternating current to energize an electricalload having a variable resistance comprising, in combination, atransformer having aprimary winding and a secondary winding,intermittent means for repeatedly interrupting the flow of the directcurrent and causing same to flow intermittently in the primary winding,and magnetic flux means to protect the intermittent means from beingoverloaded by limiting the value of the intermittent current flowing tothe primary winding when the resistance of the electrical loaddecreases.

7. A system for converting direct current into alternating current andfor utilizing the said alternating current to energize an electricalload having a variable resistance comprising, in com bination. a highleakage reactance transformer having a primary winding and a secondarywinding, and intermittent means for repeatedly interrupting the flow ofthe direct current and causing same to flow intermittently to theprimary winding, the combination of the intermittent means and the highleakage reactance transformer being such that the intermittent means isprotected from being overloaded by the action of the transformerlimiting the value of the intermittent current flowing to the primarywinding when the resistance of the electrical load decreases.

8. A system for. converting direct current into alternating current andfor utilizing the said alternating current to energize an electricalload having a variable resistance comprising, in combination, an autotransformer having two winding portions, intermittent means forrepeatedly interrupting the flow of the direct current and causing sameto flow intermittently k1 one of the winding portions, and magnetic fluxmeans to protect the intermittent means from being overloaded bylimiting the value of the intermittent current flowing to the saidwinding portion when the resistance of the electrical load decreases.

9. A system for transforming electrical energy to energize an electricalload having a variable resistance comprising, in combination, atransformer having a primary winding and a secondary winding, a tunedvibrating interrupter for causing current to flow intermittently in theprimary winding, magnetic shunt means disposed between the primary andthe secondary windings to protect the said tuned vibrating interrupterfrom being overloaded by limiting the value of the intermittent currentflowing to the primarywinding when the resistance of the electrical loaddecreases, a coil for magnetically operating the tuned vibratinginterrupter, means for energizing the coil, and automatic meansconnected in series with the coil for decreasing the energiza- 'tion 01'the coil after the tuned vibrating interrupter is set in operation.

'10. A system for transforming electrical energy to energize anelectrical load having a vaauto transformer having two winding portions,a tuned vibrating interrupter for causing current to flow intermittentlyin one of the winding portions, magnetic shunt means disposed betweenthe primary and secondary windings to protect the said tuned vibratinginterrupter from being overloaded by limiting the value of theintermittent current flowing to the said winding portion when theresistance of the electrical load decreases, a coil for magneticallyoperating the tuned vibrating interrupter, means for energizing thecoil, and automatic means connected in series with the coil fordecreasing the energize.- tion of the coil after the tuned vibratinginterrupter is set in operation.

11. A system for converting direct current into alternating current andfor utilizing the said alternating current to energize an electricalload having a variable resistance comprising, in combination, atransformer having a primary winding and a secondary winding,intermittent means for repeatedly interrupting the flow oi the directcurrent and causing same to flow intermittently in the primary winding,and magnetic shunt means disposed between the primary winding and thesecondary to protect the intermittent means from being overloaded bylimiting the value of the intermittent current flowing. to the primarywinding when the resistance of the electrical load decreases.

JAMES A. COMSTOCK. WILLIAM W. GARSTANG.

,riable resistance comprising, in combination, an

